This invention relates generally to cutting apparatus, and, more particularly, relates to apparatus for rapid cutting of metallographic specimens and other workpieces.
Certain prior art cutting devices utilize a fixed chuck for positioning a fixed workpiece at the end of an arm. The arm is then placed in a position of engagement with a rotating circular blade. As the blade cuts through the workpiece an arcuate path is created. The cutting rate typically slows, and heat increases, as the arc length increases. In sensitive materials, excess heat may cause undesirable deformation and phase changes. Moreover, cutting with this type of apparatus may require an operator to manually rotate the workpiece so that a fresh area can be cut. In the course of sectioning a workpiece, many such manual rotations may be required. The resultant section may have an irregular surface, due in part to lateral forces on the blade as the cut progresses.
An example of such a configuration is a low speed saw marketed by Buehler Ltd., which utilizes a sample chuck mounted on a pivoting arm. The sample is pressed into contact with a rotating cutting blade under the force of selectable weights.
It is known that rotating a workpiece during cutting can reduce cutting time and heating by maintaining a substantially constant small contact area between the sample and cutting wheel. Various devices have been constructed for rotating a workpiece during cutting. The following U.S. patents disclose examples of such devices.
______________________________________ 1,139,322 Anderson 2,380,178 Howlett 3,985,051 Brown 4,475,527 Kuo 4,488,463 Pontarella 4,511,826 Kouchi ______________________________________
Anderson discloses a roll trimming machine in which the roll is rotated during cutting.
Howlett discloses a cutting machine in which cutters are rotated by a first spindle, and tubular workpieces are rotated, in contact with the cutters, by a second spindle.
Brown discloses a pipe-cutting device in which workpieces are rotated in the same direction as a cutting wheel, for cutting the circumference of the pipe.
Kuo discloses ingot slicing apparatus in which the workpiece is rotated during cutting.
Pontarella discloses apparatus for stripping wire from an armature, including a circular saw for cutting wire on the armature, and a drive wheel for rotating the armature simultaneously with the cutting of the armature wire.
Kouchi et al discloses cutting apparatus including a first motor mounted on a swing arm for rotating a saw, and a second motor for rotating a workpiece to be cut.
In addition, German Patent No. 3,310,075 discloses a circular saw which rotates the sample in a direction opposite that of the blade, for reducing the contact area between the blade cutting surface and the sample surface.
A dimpling instrument commercially available from South Bay Technology, Inc., of Temple City, California utilizes a rotating chuck for holding and rotating a workpiece, and a dimpling wheel mounted on the end of a pivoting arm. The dimpling wheel can be rotated and lowered into contact with the workpiece for dimpling and polishing.
These prior art cutting devices, however, are not adapted for precise cutting of irregularly shaped workpieces.
In addition, certain conventional cutting devices utilize a rotatable workpiece chuck which is hydraulically advanced against a rotating saw blade. A cutting device of this type is commercially available from Struers, Inc., of Denmark. Cutting devices of this type cannot accommodate larger workpieces. In addition, such devices cannot follow highly irregular shaped workpieces, because the workpiece holder cannot retract when a workpiece "high spot" is encountered. The cut must progress from large radius to small radius, regardless of radial eccentricity of the workpiece.
Accordingly, there exists a need for cutting apparatus which provides reduced cutting time and improved surface finish, even for irregularly shaped or eccentrically mounted workpieces.
It is accordingly an object of the invention to provide cutting apparatus which can cut irregularly shaped or eccentrically mounted workpieces quickly and with excellent surface finish.
It is another object of the invention to provide a cutting apparatus which can cut objects of arbitrary shape with substantially constant contact area during cutting.
It is a further object of the invention to provide a cutting apparatus which can cut irregularly shaped or eccentrically mounted objects with substantially constant normal force.
Other general and specific objects of the invention will in part be obvious and will in part appear hereinafter.